This RS232 to RS485 converter is compatible with the RS232C and RS485 standard. It is able to convert RS232 signals to RS485 balanced differential signals and extend the communication distance to 1.2 km. It is a passive converter and doesn't require a external power supply. It uses a particular pump to gain power from the RS232 signals (RTS, DTR, TXD) without initializing the RS232 interface. An internal transceiver circuit automatically controls the direction of the data stream instead of handshake signals. When working in half-duplex mode the circuit keeps the same function under RS485 without any change. The transmission rate of 300 - 115200bps can be applied to point-to-point and point-to-multipoint networks.